Broad-Bodied Chaser (Libellula depressa)
These, as the name suggests, are very broad dragonflies.
They love garden ponds.  When I built my pond, one of these was checking it out within 30 minutes of me filling it with water.
Males have a blue abdomen with yellow markings at its base and a dark thorax.
Females have a golden/yellow abdomen again with yellow markings at its base and a brown thorax.
Immature ones are both similar to the female form.
It can be confused with Scare Chaser, Black Tail Skimmers and Keeled Skimmers, but as they are so broad, this is unlikely.

Male
Male
Male
Male
Male
Male
Male
Male
Male
Male
Female
Female
Female
Female
Female
Female
Female
Female
Female
Female
Female
Female
Egg Laying
Egg Laying
Egg Laying
Egg Laying
Want to See 
Widespread all over Somerset.
Garden ponds are especially a favourite.

Especially Good
I haven't really got an amazing spot to recommend.
The most I've seen at one time is at SWT Westhay (Mid May/Early June) although not in huge numbers and a bit hit or miss.

-----------------------------------